1. above) through the %" screen, rubbing the lime rock through
the screen with the hand and without jarring or shaking the
box, until the box is full. Remove the screen and strike off any
excess lime rock with a straight edge, so that the lime rock fills
the box exactly without packing or tamping.
Weigh the box full of lime rock, recording the weight to the
nearest ounce. Empty the lime rock onto the mixing slab and
re-weigh the empty box in the nearest ounce. The difference
between the two weights is the Weight of the Sample.
Sample
3. Refer to the curve (see Pages 18 and 19). The weights
appear on the left hand vertical column. With a straight edge
placed horizontally at the weight, make a dot at the intersection
of the straight edge with the curve. Then measure with a
straight edge vertically from the dot to the bottom of the page.
The number at the bottom of the page gives the water content
in % by weight. If the number is 11% or less, proceed with
(4) below. If the number is more than 11% proceed to (5)
below.
4. To the 10-lb. sample, add exactly 18 ounces of water by
weight (or by volume). Mix the water thoroughly into the
sample with a trowel or a steel rod. The sample now contains
exactly 10% extra water. Repeat (2) and (3) above. Subtract
10 from the water content to get the true per cent water content.
5. Put the original sample aside. Repeat the whole test
with another 10-lb. sample of the lime rock. If the two tests
check within 1% the results are the true water content. If they
do not check, poor sampling or carelessness in weighing are the
cause. Repeat until two good checks within 1% are obtained.
[36 ]